This invention relates to segmented tire molds and especially to molds having center segments which are movable radially in response to opening and closing of the mold.
Full segmented molds such as the mold shown and described in U.S. Pat. No. 5,585,064 provide for expanding and contracting segments, however, the segments are mounted on the top mold and must be lifted to retract the segments. In addition to the added power required to lift the segments, the wear on the parts is also a disadvantage of this type of mold.
Other segmented molds, such as the mold shown in Great Britain Patent GB 1,176,162 provide hinged segments with springs for retracting the hinge pins of the segment. The tilt type segmented molds of this type do not provide for loading an uncured tire without engaging the bridge work on the segments. This is especially objectional for molds with curved segmental boundary designs where the mold segments must be retracted in a direction perpendicular to the vertical axis of the segments.
The present invention is directed to a segmented mold having radially movable center segments which are mounted on the lower mold half. Each center segment has a slotted connection with a sloped surface of the upper mold half for retracting and then returning the segment to the registered position for molding a tire. The slot in the center segment is open at the top to permit opening of the mold without lifting of the segment. A spring holds the center segment in a radially outward position against a stop in the lower mold half which positions the slot for engagement with the upper mold half upon closing of the mold.
In accordance with one aspect of the invention there is provided a segmented tire mold having an upper mold half, a lower mold half and radially movable circumferentially spaced sliding segments characterized by:
a. each of the sliding segments being mounted on the lower mold half for radial movement,
b. a disengagable sliding connection between the upper mold half and each of the sliding segments for moving the segments radially of the mold between an open retracted position and a closed molding position.
In accordance with another aspect of the invention there is provided a method of vulcanizing a tire in a segmented tire mold having an upper mold half, a lower mold half and radially movable circumferentially spaced center segments in sliding engagement with the lower mold half and slidably engagable with the upper mold half upon closing of the mold characterized by:
a. opening the mold by lifting the upper mold half away from and out of sliding engagement with the center segments,
b. moving the center segments radially outward by the sliding engagement with the upper mold half,
c. limiting the movement of the center segments radially outward by stop means on the lower mold half,
d. placing an unvulcanized tire on the lower mold half,
e. lowering the upper mold half in sliding engagement with the center segments for moving the center segments radially inwards into engagement with the tire upon closing of the mold,
f. applying heat to the tire mold to vulcanize the tire,
g. lifting the upper mold half for sliding the center segments radially outward on the lower mold half, and
h. removing the tire from the tire mold.